JP2021002001A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device and an image forming apparatus that can reduce the size and the range of rotation of shield member and can prevent an increase in temperature of heating means.SOLUTION: A fixing device 20 has a rotatable endless rotating member (fixing belt 21), a pressure member (pressure roller) that is arranged opposite to the fixing member to form a nip part with the fixing member, heating means (halogen heater 23) that is arranged inside the fixing member, and a first shield member (movable shield member 27) and a second shield member (shield film 50) that are rotatably arranged inside the fixing member and rotated by driving means to be allowed to partially block heat directed from the heating means to the fixing member.SELECTED DRAWING: Figure 9A

Description

The present invention relates to a fixing device and an image forming device including the fixing device.

As a fixing device mounted on an image forming apparatus such as an electrophotographic copying machine or a printer, a belt type fixing device using an endless fixing belt instead of a fixing roller has been put into practical use. In such a belt-type fixing device, increasing the number of heaters corresponding to a plurality of paper sizes increases the cost and size of the device. Therefore, in general, one or two heaters are used. ing. However, when trying to handle various sizes of paper with one or two heaters, the temperature of the fixing belt rises excessively in the non-passing region due to the mismatch between the paper size and the heating range of the fixing belt. There is a problem such as doing.

In order to solve such a problem, for example, in the invention of Patent Document 1 (Japanese Unexamined Patent Publication No. 2016-95329), a shielding member is rotatably arranged around a halogen heater as a heating means, and the length of the shielding member is lengthened. The stepped shielding portions formed at both ends of the direction shield the heating range by the heating means for the non-passing paper region. Further, in the invention of Patent Document 2 (Japanese Unexamined Patent Publication No. 2013-186164), a shielding member (shielding film) is provided on the halogen heater itself as a heating means, the halogen heater is rotatably supported, and the halogen heater is rotated. Depending on the position, the heat to the non-passing area is shielded by the shielding member.

In the invention of Patent Document 1, as the types of paper widths that can be passed through the paper increase, the size of the shielding member inevitably increases and the rotation range thereof also increases, so that it becomes difficult to reduce the size of the device. On the other hand, in the invention of Patent Document 2, since light is shielded only by a shielding film having a small area close to the heater, there is a possibility that the heat resistance limit of the glass tube which is the sealing body of the halogen heater may be exceeded due to the high heat of the shielding film.

Therefore, an object of the present invention is to reduce the size of the shielding member, reduce the rotation range thereof, and suppress the temperature rise of the heating means.

In order to solve the above problems, the fixing device of the present invention includes a rotatable endless fixing member, a pressurizing member arranged to face the fixing member and forming a nip portion between the fixing member, and the above. The heating means arranged inside the fixing member and the heating means rotatably arranged inside the fixing member and rotated by the driving means can partially shield the heat from the heating means toward the fixing member. It is characterized by having a first shielding member and a second shielding member.
It is characterized by that.

According to the present invention, the first shielding member and the second shielding member can be miniaturized, the rotation range thereof can be reduced, and the temperature rise of the heating means can be suppressed.

It is the schematic of the image forming apparatus which concerns on one Embodiment of this invention. It is sectional drawing of the fixing device which concerns on one Embodiment of this invention. It is a perspective view which shows the schematic structure of the main part of the fixing device. It is a perspective view which shows the structure of one end side in which the belt holding member of the fixing device is arranged. It is a perspective view of the belt holding member. It is a perspective view which shows the structure of the drive mechanism of the movable shielding member. It is a perspective view which shows the structure of the drive mechanism of the movable shielding member. (A) is a developed view of a movable shielding member used in the embodiment of the present invention, (b) is a developed view of a shielding film, and (c) is a developed view of a conventional movable shielding member. It is a figure and the cross-sectional view of the holding member, the nip forming member and the shielding member of the fixing device which concerns on embodiment of this invention, (a) shows the state which the shielding member is in the position at the time of A3 paper passing, (b) is Indicates the state of being in the position when the postcard is passed. It is a figure and cross-sectional view of the holding member, the nip forming member and the shielding member of the conventional fixing device, (a) shows the state which the shielding member is in the position at the time of A3 paper passing, and (b) is the state at the time of postcard paper passing. Indicates the state of being in position. It is a side view of a halogen heater. It is sectional drawing of the halogen heater. It is a figure which shows the positional relationship of a halogen heater and a movable shielding member, (a) shows the time of A3 paper passing, (b) shows the time of B4 and postcard paper passing.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each drawing for explaining the embodiment of the present invention, components such as members and components having the same function or shape are once described by giving the same reference numerals as much as possible. Then, the explanation is omitted.

(Image forming device)
First, with reference to FIG. 1, the overall configuration and operation of the image forming apparatus according to the embodiment of the present invention will be described. The image forming apparatus 1 shown in FIG. 1 is a color laser printer, and four image forming portions 4Y, 4M, 4C, and 4K are provided in the center of the apparatus main body. Each image forming unit 4Y, 4M, 4C, 4K accommodates developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. It has the same configuration except that it is.

Specifically, each image processing unit 4Y, 4M, 4C, 4K is formed on a drum-shaped photoconductor 5 as a latent image carrier, a charging device 6 for charging the surface of the photoconductor 5, and the surface of the photoconductor 5. A developing device 7 for supplying toner, a cleaning device 8 for cleaning the surface of the photoconductor 5, and the like are provided. In FIG. 1, only the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8 included in the black image forming unit 4K are designated by reference numerals, and the other image forming units 4Y, 4M, and 4C have reference numerals. The code is omitted.

An exposure device 9 that exposes the surface of the photoconductor 5 is arranged below each image forming unit 4Y, 4M, 4C, 4K. The exposure device 9 has a light source, a polygon mirror, an f−θ lens, a reflection mirror, and the like, and irradiates the surface of each photoconductor 5 with laser light based on the image data.

Further, a transfer device 3 is arranged above each image forming unit 4Y, 4M, 4C, 4K. The transfer device 3 includes an intermediate transfer belt 30 as an intermediate transfer body, four primary transfer rollers 31 as a primary transfer means, a secondary transfer roller 36 as a secondary transfer means, a secondary transfer backup roller 32, and the like. A cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35 are provided.

The intermediate transfer belt 30 is an endless belt, and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, by rotationally driving the secondary transfer backup roller 32, the intermediate transfer belt 30 orbits (rotates) in the direction indicated by the arrow in the figure.

Each of the four primary transfer rollers 31 has an intermediate transfer belt 30 sandwiched between the four primary transfer rollers 31 and each of the photoconductors 5 to form a primary transfer nip. A power supply is connected to each primary transfer roller 31, and a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to each primary transfer roller 31.

The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Further, similarly to the primary transfer roller 31, a power supply is also connected to the secondary transfer roller 36, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to the secondary transfer roller 36. ..

The belt cleaning device 35 has a cleaning brush and a cleaning blade arranged so as to abut the intermediate transfer belt 30. The waste toner collected by the belt cleaning device 35 is stored in the waste toner container via the waste toner transfer hose.

A bottle accommodating portion 2 is provided in the upper part of the image forming apparatus main body, and four toner bottles 2Y, 2M, 2C, and 2K accommodating replenishing toner are detachably attached to the bottle accommodating portion 2. ing. Toner is replenished from each toner bottle 2Y, 2M, 2C, 2K to each developing device 7 via a replenishment path provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7.

On the other hand, in the lower part of the image forming apparatus main body, a paper feed tray 10 containing the paper P as a recording medium, a paper feed roller 11 for carrying out the paper P from the paper feed tray 10, and the like are provided. In addition to plain paper, the recording medium includes thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, and the like. Further, a manual paper feed mechanism may be provided.

In the image forming apparatus main body, a transport path R for passing the paper P from the paper feed tray 10 through the secondary transfer nip and discharging it to the outside of the apparatus is arranged. In the transport path R, a pair of resist rollers 12 as timing rollers for transporting the paper P to the secondary transfer nip at the transfer timing are arranged on the upstream side in the paper transport direction from the position of the secondary transfer roller 36. There is.

Further, a fixing device 20 for fixing the unfixed image transferred to the paper P is arranged on the downstream side in the paper transport direction from the position of the secondary transfer roller 36. Further, a pair of paper ejection rollers 13 for ejecting the paper to the outside of the apparatus are provided on the downstream side of the transport path R in the paper transport direction with respect to the fixing device 20. Further, a paper ejection tray 14 for stocking the paper ejected outside the apparatus is provided on the upper surface of the apparatus main body.

Subsequently, the basic operation of the printer according to the present embodiment will be described with reference to FIG. When the image-drawing operation is started, each photoconductor 5 in each image-forming unit 4Y, 4M, 4C, 4K is rotationally driven clockwise in the figure, and the surface of each photoconductor 5 is brought to a predetermined polarity by the charging device 6. It is uniformly charged.

The surface of each charged photoconductor 5 is irradiated with laser light from the exposure device 9, and an electrostatic latent image is formed on the surface of each photoconductor 5. At this time, the image information to be exposed to each photoconductor 5 is monochromatic image information obtained by decomposing a desired full-color image into yellow, magenta, cyan, and black color information. By supplying toner to the electrostatic latent image formed on each photoconductor 5 in this way by each developing device 7, the electrostatic latent image is visualized (visualized) as a toner image. ..

Further, when the image-drawing operation is started, the secondary transfer backup roller 32 is rotationally driven counterclockwise in the drawing to rotate the intermediate transfer belt 30 in the direction indicated by the arrow in the figure. Further, by applying a constant voltage or a constant current controlled voltage opposite to the charging polarity of the toner to each primary transfer roller 31, the primary transfer nip between each primary transfer roller 31 and each photoconductor 5. A transfer electric field is formed in.

After that, when the toner image of each color on the photoconductor 5 reaches the primary transfer nip as the photoconductor 5 rotates, the toner image on each photoconductor 5 is generated by the transfer electric field formed in the primary transfer nip. Is sequentially superposed on the intermediate transfer belt 30 and transferred. Thus, a full-color toner image is supported on the surface of the intermediate transfer belt 30. Further, the toner on each photoconductor 5 that could not be completely transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. Then, the surface of each photoconductor 5 is statically eliminated by the static elimination device, and the surface potential is initialized.

At the lower part of the printer, the paper feed roller 11 starts rotational driving, and the paper P is sent out from the paper feed tray 10 to the transport path R. The paper P sent out to the transport path R is temporarily stopped by the resist roller 12.

After that, the rotational drive of the resist roller 12 is started at a predetermined timing, and the paper P is conveyed to the secondary transfer nip at the timing when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, whereby a transfer electric field is formed in the secondary transfer nip. ..

Then, the toner image on the intermediate transfer belt 30 is collectively transferred onto the paper P by this transfer electric field. Further, the residual toner on the intermediate transfer belt 30 that could not be transferred to the paper P at this time is removed by the belt cleaning device 35 and conveyed to the waste toner container.

After that, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is fixed to the paper P by the fixing device 20. Then, the paper P is discharged to the outside of the device by the paper ejection roller 13 and is stocked on the paper ejection tray 14.

The above description is an image forming operation when forming a full-color image on paper, but a single-color image can be formed by using any one of four image forming units 4Y, 4M, 4C, and 4K. It is also possible to form a two-color or three-color image using two or three image-forming sections.

(Fixing device)
FIG. 2 is a cross-sectional view of the fixing device 20 according to the present embodiment. As shown in FIG. 2, the fixing device 20 serves as a fixing belt 21 as a fixing member, a pressure roller 22 as a pressure member facing the outer peripheral surface of the fixing belt 21, and a heating means for heating the fixing belt 21. Halogen heater 23, a nip forming member 24 arranged on the inner peripheral side of the fixing belt 21, a stay 25 as a support member for supporting the nip forming member 24, and heat (radiant heat) radiated from the halogen heater 23. A reflective member 26 that reflects light to the fixing belt 21, a movable shielding member 27 as a first shielding member that shields heat (radiant heat) or light radiated from the halogen heater 23, and both ends of the halogen heater 23 are formed. A shielding film 50 as a second shielding member, a fixed shielding member 28 that shields heat (radiant heat) or light radiated from the halogen heater 23, and a temperature sensor 29 as a temperature detecting means for detecting the temperature of the fixing belt 21. Etc.

The fixing belt 21 is formed of a thin and flexible endless belt member (including a film). Specifically, the fixing belt 21 is formed of a base material on the inner peripheral side formed of a metal material such as nickel or SUS or a resin material such as polyimide (PI), and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). Alternatively, it is composed of a release layer on the outer peripheral side formed of polytetrafluoroethylene (PTFE) or the like. An elastic layer made of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber may be interposed between the base material and the release layer.

If there is no elastic layer, the heat capacity becomes smaller and the fixability can be improved, but when the unfixed toner is crushed and fixed, the minute irregularities on the belt surface are transferred to the image and the solid part of the image becomes unevenly glossy. It can occur. In order to prevent this, it is desirable to provide an elastic layer having a thickness of 100 μm or more. By providing an elastic layer having a thickness of 100 μm or more, it is possible to absorb minute irregularities due to elastic deformation of the elastic layer, so that it is possible to avoid the occurrence of uneven gloss.

In the present embodiment, the fixing belt 21 is thin and has a small diameter in order to reduce the heat capacity of the fixing belt 21. Specifically, the thicknesses of the base material, the elastic layer, and the release layer constituting the fixing belt 21 are set in the ranges of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the overall thickness is set. It is set to 1 mm or less.

The diameter of the fixing belt 21 is set to 20 to 40 mm. In order to further reduce the heat capacity, it is desirable that the thickness of the entire fixing belt 21 is 0.2 mm or less, and more preferably 0.16 mm or less.

The pressure roller 22 is provided on the surface of the core metal 22a, the elastic layer 22b made of a rubber material such as foamable silicone rubber, silicone rubber, or fluororubber provided on the surface of the core metal 22a, and the elastic layer 22b. It is composed of a release layer 22c made of PFA, PTFE or the like. The pressurizing roller 22 is pressurized to the fixing belt 21 side by the pressing mechanism, and is in contact with the nip forming member 24 via the fixing belt 21. At the position where the pressure roller 22 and the fixing belt 21 are in pressure contact with each other, the elastic layer 22b of the pressure roller 22 is crushed to form a nip portion N having a predetermined width.

Further, the pressurizing roller 22 is configured to be rotationally driven by a drive source such as a motor provided in the main body of the apparatus. When the pressure roller 22 rotates, the driving force thereof is transmitted to the fixing belt 21 by the nip portion N, and the fixing belt 21 rotates in a driven manner.

In the present embodiment, the pressure roller 22 is a solid roller, but it may be a hollow roller. In that case, a heating means such as a halogen heater may be arranged inside the pressurizing roller 22. Further, the elastic layer 22b may be solid rubber, but if there is no heating means inside the pressure roller 22, sponge rubber may be used. Sponge rubber is more preferable because it has higher heat insulating properties and is less likely to take away heat from the fixing belt 21.

The halogen heater 23 is arranged on the inner peripheral side of the fixing belt 21 and directly heats the fixing belt 21 at a place other than the nip portion N. In the present embodiment, the halogen heater 23 directly faces the fixing belt 21 in the region on the upstream side in the paper transport direction in the fixing belt 21, and the fixing belt 21 is directly heated in the region on the upstream side.

Further, the halogen heater 23 generates heat by controlling the output by a power supply unit provided in the main body of the apparatus. The output control is performed based on the detection result of the surface temperature of the fixing belt 21 by the temperature sensor 29.

By controlling the output of the heater 23 in this way, the fixing belt 21 is maintained at a desired temperature (fixing temperature). In addition, instead of the temperature sensor that detects the temperature of the fixing belt 21, a temperature sensor that detects the temperature of the pressurizing roller 22 is provided, and the temperature of the fixing belt 21 is predicted by the temperature detected by the temperature sensor. May be good.

When fixing the unfixed image T supported on the paper P, first, the rotary drive of the pressurizing roller 22 is started to drive the fixing belt 21 to rotate, and the halogen heater 23 is heated to heat the fixing belt 21. To do. Then, in a state where the temperature of the fixing belt 21 has risen to a desired temperature, the unfixed image T (toner) on the paper P is heated and pressurized by passing the paper P through the nip portion N. Be fixed.

In the present embodiment, one halogen heater is used, but the number of halogen heaters is set to two or more according to the size of the paper used in the printer, and a shielding film 50 is formed on each of the two or more halogen heaters. You may. Further, as a heating means for heating the fixing belt 21 by using radiant heat, a carbon heater or the like can be used in addition to the halogen heater.

The nip forming member 24 is arranged inside the fixing belt 21 and at a position facing the pressure roller 22 via the fixing belt 21. The nip forming member 24 has a base material 241 and a heat conductive member 242. The base material 241 is made of a resin material having high heat resistance, such as polyethersulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyethernitrile (PEN), polyamideimide (PAI), and polyetheretherketone. It is made of (PEEK) or the like.

On the other hand, the thermal conductivity member 242 is a member having a thermal conductivity larger than that of the base material 241 such as carbon nanotubes (thermal conductivity: 3000 to 5500 W / mK), graphite sheet (thermal conductivity: 700 to 1750 W / mK), and silver. It is made of (thermal conductivity: 420 W / mK), copper (thermal conductivity: 398 W / mK), aluminum (thermal conductivity: 236 W / mK), SECC (electrozinc plated steel), or the like. The thermal conductivity of the heat conductive member 242 is preferably 236 W / mK or more.

The heat conductive member 242 is arranged on the nip portion N side of the base material 241. Further, the base material 241 is supported by the stay 25. As a result, it is possible to prevent the nip forming member 24 from bending due to the pressure applied by the pressurizing roller 22, and to form a uniform nip width in the entire axial direction of the opposite region between the fixing belt 21 and the pressurizing roller 22. .. The stay 25 is made of a metal material such as a steel material such as stainless steel in order to satisfy the bending prevention function of the nip forming member 24. However, if the stay 25 is sufficiently effective in preventing bending, the stay 25 is formed of a resin material. You may.

Further, a low friction sheet is attached to the surface of the heat conductive member 242 on the N side of the nip portion. When the fixing belt 21 rotates, the inner peripheral surface of the fixing belt 21 slides against the low friction sheet, so that the frictional resistance acting on the fixing belt 21 can be reduced. It is also possible to omit the low friction sheet.

The reflective member 26 is arranged between the stay 25 and the halogen heater 23, and is fixedly supported by the stay 25. By reflecting the heat from the halogen heater 23 to the fixing belt 21 by the reflecting member 26, the heat is suppressed from being transferred to the stay 25 and the like, and the fixing belt 21 can be efficiently heated to save energy. I'm trying.

As the material of the reflective member 26, aluminum, stainless steel, or the like is used. In particular, when silver having a low emissivity (high reflectance) is deposited on an aluminum base material, the heating efficiency of the fixing belt 21 can be improved.

(Movable shielding member and fixed shielding member)
The movable shielding member 27, which is the first shielding member, is configured by forming, for example, a metal plate having a thickness of 0.1 mm to 1.0 mm in an arcuate cross-sectional shape along the inner peripheral surface of the fixing belt 21. There is. Further, the movable shielding member 27 is configured to be rotatable in the circumferential direction between the fixing belt 21 and the halogen heater 23.

On the other hand, the fixed shielding member 28 is fixed to the stay 25. The fixed shielding members 28 are arranged on both end sides of the fixing belt 21 and cover the fixing belt 21 side of the halogen heater 23. For both the movable shielding member 27 and the fixed shielding member 28, it is preferable to use a metal material such as aluminum, iron, stainless steel, or ceramic having heat resistance.

FIG. 3 is a perspective view showing a schematic configuration of a main part of the fixing device 20 according to the present embodiment. As shown in FIG. 3, the movable shielding member 27 has a pair of shielding portions 271 arranged on both end sides in the width direction thereof, and a connecting portion 272 that connects the shielding portions 271 to each other. The shielding portion 271 is a portion that shields heat to the fixing belt 21, and is formed in an arc shape in the circumferential direction along the inner peripheral surface of the fixing belt 21.

The connecting portion 272 is formed shorter than the shielding portion 271 in the circumferential direction, and is connected to the upstream side of each shielding portion 271 in the belt rotation direction. Therefore, the portion (downstream side in the belt rotation direction and the intermediate portion) where the connecting portion 272 does not intervene between the shielding portions 271 is an open portion through which the light from the halogen heater 23 is transmitted.

(Rotating support structure of fixing belt)
As shown in FIG. 3, belt holding members 40 are inserted on the inner peripheral sides of both ends of the fixing belt 21. The fixing belt 21 is rotatably supported by belt holding members 40 on both ends thereof, and basically there is no member other than the belt holding member 40 that supports the fixing belt 21.

That is, the fixing belt 21 is in a non-tensioned state in which it is not bridged by a roller or the like. The belt holding member 40, together with the halogen heater 23 and the stay 25, is fixedly supported by a pair of side plates provided on both sides of the fixing belt 21 in the axial direction.

FIG. 4 is a perspective view showing a configuration on one end side where the belt holding member of the fixing device 20 is arranged, and FIG. 5 is a perspective view of the belt holding member. As shown in FIGS. 4 and 5, the belt holding member 40 includes a holding portion 401 that rotatably holds the fixing belt 21, a regulating portion 402 that regulates the axial deviation of the fixing belt 21, and a fixing device 20. It has a fixing portion 403 fixed to the side plate 39 with a fastener such as a screw.

The holding portion 401 is formed in a partially cylindrical shape having an opening 404 in a part in the circumferential direction. By inserting the holding portion 401 into the end portion of the fixing belt 21, the fixing belt 21 is rotatably held by the holding portion 401.

As shown in FIG. 4, in the state where each member is assembled, the end portion of the nip forming member 24 is arranged in the opening 404 of the holding portion 401. Further, a fixed shielding member 28 is arranged on the inner peripheral side of the holding portion 401. As a result, the belt holding member 40 is prevented from excessively rising in temperature due to the heat from the halogen heater 23, and deformation or breakage due to the heat is prevented.

The regulating portion 402 is formed to be at least larger than the outer diameter of the fixing belt 21. As shown in FIG. 5, the fixing belt 21 is arranged with its end facing the regulating portion 402. Then, when the fixing belt 21 is moved in the axial direction during driving, the end portion of the fixing belt 21 comes into contact with the regulating portion 402 to regulate the moving.

(Fixing belt drive mechanism)
6 and 7 are perspective views showing the configuration of the drive mechanism of the movable shielding member 27. As shown in FIG. 6, the movable shielding member 27 is supported via an arc-shaped slide member 41 attached to the belt holding member 40.

In the present embodiment, the movable shielding member 27 is attached to the slide member 41 by inserting the protrusion 270 provided at the end portion of the movable shielding member 27 into the hole portion 410 provided in the slide member 41. Further, the slide member 41 is provided with a convex portion 411, and the convex portion 411 is inserted into the arcuate groove portion 405 provided on the belt holding member 40, so that the slide member 41 slides along the groove portion 405. It is configured to be movable. As a result, the movable shielding member 27 is configured to be integrally reciprocating with the slide member 41 in the circumferential direction of the belt holding member 40.

Further, as shown in FIG. 7, the slide member 41 is provided with a gear portion 412 in the circumferential direction thereof. A motor M1 which is a drive source is connected to the gear portion 412 via a gear train composed of a plurality of transmission gears 43, 44, 45. As a result, when the motor M1 is driven, the driving force is transmitted to the slide member 41 via the gear trains (transmission gears 43, 44, 45), and the movable shielding member 27 rotates in the forward and reverse directions.

(Details of movable shielding member)
FIG. 8A shows a developed view of the movable shielding member 27. The movable shielding member 27 has stepped shielding portions 271 at both ends in the longitudinal direction, and these shielding portions 271 are connected by narrow connecting portions 272. The step-shaped shielding portion 271 has a first shielding portion 271a and a second shielding portion 271b, and an opening corresponding to A3 is formed between the first shielding portions 271a. Further, a B4 compatible opening is formed between the second shielding portions 271b.

FIG. 8C shows a developed view of the conventional movable shielding member 27, in which the stepped shielding portion 271 has a third shielding portion 271c in addition to the first shielding portion 271a and the second shielding portion 271b. An opening corresponding to a postcard is formed between the third shielding portions 271c. In the embodiment of the present invention, the shielding film 50, which is the second shielding member of the halogen heater 23, eliminates the need for the conventional third shielding portion 271c, and the movable shielding member 27 is reduced in size and movement amount by that amount. It is unique in that.

Further, FIG. 8B shows a developed view of the shielding film 50 formed at both ends of the halogen heater 23. The three parts A to C correspond to the parts A to C of FIGS. 10A and 10B described later. The shielding film 50 extends from a base end portion corresponding to the edge portion of the first shielding portion 271a of the A3 compatible opening to a tip portion corresponding to the edge portion of the third shielding portion 271c of the postcard-compatible opening.

The shielding film 50 has a trapezoidal shape as a whole, and the circumferential angle of the inner end portion is 180 °, and the circumferential angle of the base end portion is 360 °. Therefore, the shielding film 50 is composed of a horizontally long rectangular main shielding portion 50a and a right triangle auxiliary shielding portion 50b so as to be divided into upper and lower parts by the broken line in FIG. 8B.

FIG. 9A is a perspective view of a fixing device 20 using the movable shielding member 27 of FIG. 8A and the halogen heater 23 having the shielding film 50 according to the present embodiment. 9B is a perspective view of the fixing device 20 using the conventional movable shielding member 27 of FIG. 8B. The hatched portion of the movable shielding member 27 shown in each (a) of FIGS. 9A and 9B indicates a shielding portion during A3 paper passing, and the hatched portion of the movable shielding member 27 shown in each (b) is used during postcard passing. Shows the shielded part.

The movable shielding member 27 of the present embodiment can take two positions, the first position in FIG. 9A (a) and the second position in FIG. 9A (b). The first position minimizes the shielding region of the movable shielding member 27, and the second position maximizes the shielding region of the movable shielding member 27. On the other hand, the conventional movable shielding member 27 can take a position corresponding to a postcard in addition to FIGS. 9B (a) and 9B (b).

The movable shielding member 27 moves according to the size of the paper P to shield an unnecessary area (non-passing area). As a result, even when the paper P having a narrow paper width is continuously passed, the so-called overheated state in which the non-passing region becomes unnecessarily high is suppressed.

Therefore, it is not necessary to perform control such as lowering the productivity in order to avoid an excessively high temperature state. Further, this makes it possible to reduce the number of halogen heaters from, for example, two to one, reduce the production cost, and contribute to energy saving.

Assuming that the rotation angle from the first position to the second position is Y1 in FIG. 9A of the present embodiment and Y2 in the conventional FIG. 9B, there is a relationship of Y1 <Y2. That is, in the present embodiment, Y1 <Y2 is set by reducing the movement range of the movable shielding member 27 by the amount of movement to the postcard-compatible position.

(Light-shielding film for halogen heater)
FIG. 10A is a side view of the halogen heater 23 on which the shielding film 50 is formed. Further, FIG. 10B shows a cross section at three portions A to C in the longitudinal direction of FIG. 10A. Shielding films 50 are provided at both ends of the halogen heater 23. Since the shielding film 50 is viewed from the side surface, it looks like a right triangle in FIG. 10A, but in the case of the illustrated configuration, the plane development shape is trapezoidal as shown in FIG. 8B. The part C in FIGS. 10A and 10B corresponds to the upper base of the trapezoid.

Therefore, the shielding angle by the shielding film 50 changes linearly from the minimum to the maximum, but of course, a shape other than the one shown in the figure is adopted, and the shielding angle changes, for example, in a stepped shape so as not to be linear. It doesn't matter. In this example, the shielding film 50 does not exist anywhere in the circumferential direction of the heater 23 in the range of L3 (for example, a large postcard width) which is the minimum paper size, and is provided from the region of reference numeral C to the region of reference numeral A. is there.

FIG. 10B is a cross-sectional view of the heater 23 corresponding to the three portions A to C in FIG. 10A. As can be seen from FIG. 10B, the light-shielding angle of the shielding film 50 is the narrowest at the portion C on the distal end side (θ1 = about 180 °) and the widest at the portion A on the proximal end side (θ2 = 360 °). ..

As the material of the shielding film 50, a molybdenum alloy, aluminum foil, or the like can be used. Moreover, silver vapor deposition may be used. As a method of fixing the shielding film 50 to the halogen heater 23, various methods such as vapor deposition, adhesion, and coating can be adopted, and any method can be adopted as long as the temperature of the stay 25 and the reflective member 26 can be reduced. Good. If the surface of the shielding film 50 on the halogen heater 23 side is configured to reflect infrared rays, the heat generation efficiency is improved, and it is possible to shorten the warm-up time and save energy.

Further, in the illustrated example, the shielding film 50 is formed on the surface of the sealed body made of the glass tube of the halogen heater 23, but the shielding film 50 may be formed by providing a gap with the surface of the sealed body. This also makes it possible to provide directivity by heat radiation from the halogen heater 23 and reduce the temperatures of the stay 25 and the reflective member 26.

The halogen heater 23 of FIG. 10A is configured to be rotatable in a range of 180 ° by a driving means such as a motor M2 connected to one end in the longitudinal direction. As a result, the side with the shielding film 50 is turned to the reflecting member 26 side as shown in FIG. 9A (a), so that the heat at both ends of the halogen heater 23 is irradiated to the fixing belt 21 without being blocked by the shielding film 50. Can be done. That is, when the movable shielding member 27 is in the first position in FIG. 9A (a), the fixing belt 21 can be heated over almost the entire length of the halogen heater 23.

On the other hand, by rotating the halogen heater 23 by 180 ° by the driving means and setting the side where the shielding film 50 is located to the fixing belt 21 side as shown in FIG. 9A (b), the heat at both ends of the halogen heater 23 is transferred to the shielding film 50. Can be shielded with. That is, when the movable shielding member 27 is in the second position in FIG. 9A (b), the innermost portion of both ends of the halogen heater 23 is shielded by the shielding film 50 (main shielding portion 50a), and the movable shielding member 27 is shielded. The outer portion can be shielded by the second shielding portion 271b of the movable shielding member 27 so as to overlap the shielding film 50. Therefore, as shown in FIG. 11B, a limited heating region corresponding to postcards is formed between the shielding films 50, and the fixing belt 21 can be heated without causing an abnormal temperature rise in the non-paper-passing portion.

The rotation direction when the halogen heater 23 is rotated by the driving means by 180 ° is the direction in which the movable shielding member 27 is rotated from the first position in FIG. 9A (a) to the second position in FIG. 9A (b) (counterclockwise). ) And the opposite direction (clockwise). In this way, by making the rotation directions of the movable shielding member 27 which is the first shielding member and the shielding film 50 which is the second shielding member opposite to each other, the rotation distance between the movable shielding member 27 and the halogen heater 23 Can be minimized to save space.

The angle Y1 when the movable shielding member 27 rotates from the first position in FIG. 9A (a) to the second position in FIG. 9A (b) is smaller than the reversal angle (X = 180 °) of the halogen heater 23 (X = 180 °). Y1 <X). The reduced rotation angle of the movable shielding member 27 is supplemented by the shielding film 50 of the halogen heater 23. As a result, the movable shielding member 27 can be miniaturized and the rotation range can be reduced, while the shielding film 50 can be made smaller than the invention of the conventional patent document 2 to avoid the increase in heat.

Here, assuming that the irradiation range (about 120 °) by the reflection member 26 is X, the movable range of the movable shielding member 27 is Y, and the rotation range (180 °) of the halogen heater 23 is Z in FIG. 9A, Y + Z> X. It is desirable to establish a relationship. That is, as shown in FIG. 9A (b), the halogen heater 23 reflected by the shielding film 50 in a state where both ends of the halogen heater 23 are covered with the shielding film 50 of the halogen heater 23 and the second shielding portion 271b of the movable shielding member 27. A gap for heat release is formed at the circumferential end of the reflective member 26 so that the heat of the above does not stay in the narrow space between the reflective member 26 and the reflective member 26. This makes it possible to prevent the temperature of the reflective member 26 from exceeding the heat resistant temperature.

(Positional relationship between halogen heater and movable shielding member)
11 (a) and 11 (b) are views showing the positions of the movable shielding member 27 when various sizes of paper are fixed. FIG. 11A shows the first position of the movable shielding member 27, and FIG. 11B shows the second position. The A3 paper having the maximum width is fixed at the first position in FIG. 11 (a), and the B4 paper is fixed at the second position in FIG. 11 (b).

Further, for fixing the large postcard paper, which is the minimum width paper, as shown by the broken line in FIG. 11B, the shielding film 50 of the halogen heater 23 is rotated toward the fixing belt 21 side (front side in the drawing) to the second position. Do it with. Therefore, the movable shielding member 27 may be moved between FIGS. 11A and 11B, and the moving distance of the movable shielding member 27 is reduced as compared with the conventional case to minimize the empty space of the circumferential movement path. be able to.

The rotation of the movable shielding member 27 and the halogen heater 23 may be performed individually based on a signal from the temperature sensor 29 that detects the temperature of the fixing belt 21, apart from the selection of various sizes of paper to be fixed. .. Thereby, the temperature control of the fixing belt 21 can be further optimized. Further, the motor M1 that rotationally drives the movable shielding member 27 and the motor M2 that rotationally drives the halogen heater 23 can be integrated into one motor by sharing. This makes it possible to reduce costs by reducing the number of parts.

If the halogen heater 23 does not have the shielding film 50 in the state of FIG. 9A (a) described above, and if the lighting rate of the halogen heater 23 is high and continuous as in the case of continuous paper passing through the paper P, the reflective member The surface temperature of 26 can be 300 ° C. or higher. As a result, the mirror surface treatment on the surface of the reflective member 26 may be discolored, or the surface layer may be peeled off when the mirror surface treatment is performed by thin film deposition.

On the other hand, when the shielding film 50 is formed on the halogen heater 23, the reflective member 26 is formed even when the lighting rate of the halogen heater 23 is high and continuous as shown in FIG. 9A (a) in which the paper P is continuously passed. It is also possible to obtain the effect that the surface temperature on the halogen heater 23 side of the above can be, for example, less than 250 ° C.

Although the present invention has been described above, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. In the above-described embodiment, the paper sizes of large postcards, B4, and A3 have been described, but the configuration of the present invention is also applied to a fixing device that supports paper such as letter vertical size and double letter vertical size. It is possible. Further, the image forming apparatus 1 equipped with the fixing apparatus 20 according to the present invention is not limited to the color printer as shown in FIG. 1, and may be a monochrome printer. Further, the present invention is not limited to a printer, and may be a copying machine, a facsimile, or a multifunction device thereof.

1: Image forming device 2: Bottle housing
2Y, 2M, 2C, 2K: Toner bottle 3: Transfer device
4Y, 4M, 4C, 4K: Image-creating part 5: Photoreceptor 6: Charging device 7: Developing device 8: Cleaning device 9: Exposure device 10: Paper feed tray 11: Paper feed roller 12: Resist roller 13: Paper discharge roller 14: Paper discharge tray 20: Fixing device 21: Fixing belt 22: Pressurizing roller 22a: Core metal 22b: Elastic layer 22c: Release layer 23: Halogen heater (heating means)
24: Nip forming member 25: Stay 26: Reflective member 27: Movable shielding member (first shielding member)
28: Fixed shielding member 29: Temperature sensor 30: Intermediate transfer belt 31: Primary transfer roller 32: Secondary transfer backup roller 33: Cleaning backup roller 34: Tension roller 35: Belt cleaning device 36: Secondary transfer roller 39: Side plate 40 : Belt holding member 41: Slide members 43, 44, 45: Transmission gear 50: Shielding film (second shielding member)
241: Base material 242: Heat conductive member 270: Protrusion 271: Shielding part 271a: First shielding part 271b: Second shielding part 272: Connecting part 401: Holding part 402: Regulatory part 403: Fixed part 404: Opening 405: Groove 410: Hole 411: Convex 412: Gear M1, M2: Motor N: Nip P: Paper R: Conveyance path

Japanese Unexamined Patent Publication No. 2016-95329 Japanese Unexamined Patent Publication No. 2013-186164

Claims (9)

With a rotatable endless fixing member
A pressurizing member arranged to face the fixing member and forming a nip between the fixing member and
The heating means arranged inside the fixing member and
It has a first shielding member and a second shielding member that are rotatably arranged inside the fixing member and can partially shield heat from the heating means toward the fixing member by being rotated by a driving means. A fixing device characterized by this. The fixing device according to claim 1, wherein the first shielding member is arranged between the heating means and the fixing member, and the second shielding member is arranged in contact with the heating means. The fixing device according to claim 1 or 2, wherein the first shielding member and the second shielding member rotate independently by a dedicated driving means, respectively. The fixing device according to claim 1 or 2, wherein the first shielding member and the second shielding member rotate by a common driving means. 3. A third aspect of the present invention, which comprises a detecting means for detecting the temperature of the fixing member, and the first shielding member and the second shielding member are driven by the driving means based on the detection result of the detecting means. Or the fixing device of 4. Any one of claims 1 to 5, wherein the first shielding member and the second shielding member rotate in opposite directions when partially shielding the heating region of the heating means. Fixing device. Any of claims 1 to 6, wherein the heating means is composed of a halogen heater, and the second shielding member is formed as a shielding film on the outer peripheral surface or the inner peripheral surface of the sealed body of the halogen heater. The fixing device of item 1. A part of the non-passing area when passing the minimum width paper that can be passed through the nip portion is shielded by the first shielding member, and the remaining non-passing area is shielded by the second shielding member. The fixing device according to any one of claims 1 to 7, characterized in that. An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 8.

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